Predictors of medication nonadherence among hypertensive clients in a Ghanaian population: Application of the Hill‐Bone and Perceived Barriers to Treatment Compliance Scale

Abstract Background and Aim Nonadherence to antihypertensive medication impairs optimal blood pressure and is influenced by multiple interrelating factors. Knowing the complexity of medication nonadherence and its associated factors is essential for intervention strategies. This study evaluated the predictors of medication nonadherence among hypertensive clients in a Ghanaian population. Methods This was a hospital‐based cross‐sectional study conducted at the Hypertensive Clinic of the Kwame Nkrumah University of Science and Technology (KNUST) Hospital, Kumasi, Ghana. A self‐designed questionnaire, the Hill‐Bone Compliance to High Blood Pressure Therapy and Perceived Barriers to Treatment Compliance Scales, were used for data collection from 246 hypertensives. Data were analyzed using Statistical Package for Social Sciences, version 25. Results Medication nonadherence was observed among 8.5% of the study participants. In a multivariate regression model perceived noneffectiveness of medication (odds ratio [OR] = 1.76, 95% confidence interval [CI]: 1.34–2.31, p < 0.001) and barriers to alcohol and smoking cessation (OR = 2.83, 95% CI: 1.31–6.13, p = 0.008) were associated increased odds of antihypertensive medication nonadherence. Also, patients who do not know their total prescription (OR = 8.81, 95% CI: 2.28–34.0, p = 0.002) were more likely to be nonadherent to their antihypertensive medications. Moreover, clients who associate signs/symptoms of palpitations (OR = 5.82, 95% CI: 1.31–25.80, p = 0.021), poor sleep (OR = 3.92, 95% CI: 1.09–14.12, p = 0.036) and decreased sexual drive (OR = 4.74, 95% CI: 0.96–23.28, p = 0.055), were more likely to be nonadherent to antihypertensive medication. Conclusion In conclusion, we observed a lower nonadherence rate among hypertensive clients in a Ghanaian population with correlates being medication‐related factors. Most importantly, perceived noneffectiveness of medication, barriers to smoking and alcohol cessation, palpitations, poor sleep, and decreased sexual drive significantly predicted lower adherence and could serve as indicators for high risk of nonadherence to antihypertensive medications.

sexual drive significantly predicted lower adherence and could serve as indicators for high risk of nonadherence to antihypertensive medications. More recently, less than half of hypertensive clients in Ghana are aware of their hypertensive status. 3 With the constantly alarming figures of HPT in general and especially in Ghana, common behavioral changes represent a lowcost alternative for prevention. Besides, among those living with HPT, diagnosis, initiation, and retention to care and adherence to both pharmacological and nonpharmacological therapy are essential for reducing consequent cardiovascular complications. 4 Notwithstanding the existence of vast evidence on the advantages of HPT treatment, control of blood pressure (BP) has been disappointing.
Various studies have reported that BP control among hypertensive clients in Ghana is mainly poor due to noncompliance to therapy. 5 Previous studies have established the high prevalence of uncontrolled HPT in Ghana, 2,6,7 however, there is limited data on correlates that influence HPT control in the Ghanaian hypertensive population. 3,5 Thus, assessing medication adherence and its correlates is vital to ascertain and monitor treatment and its outcomes to reduce HPT-related mortality.
It is essential to admit that addressing medication adherence is essential and disreputably difficult in practice. Sometimes, clients are unable to give accurate reports of their adherence to medication. It has been shown that less than 50% of hypertensive patients that are initiated to care, take their medications as prescribed. 3,8 To-wit interviewing clients using questinnaires represents a powerful tool for ascertaining clients' concepts and behavior regarding medication adherence. These tools represent an easy-to-use, low-cost subjective method to survey clients' medication-taking behavior and possible factors that influence their decision. They are designed to standardize and minimize the limitations of other self-reported adherence measurement methods to a specific medication regime. 9

| Eligibility criteria
Participants who had been diagnosed with HPT and are on treatment for at least 6 months attending the hypertensive clinic of KNUST Hospital and gave written consent were recruited into the study.
Clients who have been on treatment for less than 6 months were excluded from the study. Also, clients who were transferred in or not registered at the KNUST hospital for regular appointment schedules were excluded from the study. Clients who had confirmed comorbidities such as diabetes mellitus, heart diseases, renal diseases were also excluded.

| Sample size justification
The sample size for this study was calculated using the formula described by Charan and Biswas. 10 Using 58.6% as the rate of noncompliance to antihypertensive treatment from our previous study, 3 with a standard normal variate of 1.96 (at 5% type-1 error), 0.05 precision and 65% response rate, the least estimated sample size for the study was 242 from a total estimated population of 600 clients over 6 months period. Accordingly, a sample size of 246 was finally used.

| Data collection
Data were collected from September 2018 to February 2019.
Participants were recruited using the convenient sampling method.
Hypertensive clients who did not consent or were seriously ill (too sick to be interviewed) were excluded from the study. For all included participants, a questionnaire interview was conducted using a structured close-ended questionnaire to collect data on demography, therapy adherence, perceived barriers, and symptoms/side effects of medication. The entire questionnaires were available in the English version but were interviewed carefully with the proper translation of the official local language of the study population. The participants' responses were translated back to English in the correct meaning as was interpreted.

| Sociodemographic questionnaire
The questionnaire consisted of items that assessed the participants' details and medication history. Besides, the questionnaire contained sections that evaluated medication's most frequently perceived side effects from the past 3 months before data collection.

| Hill-Bone Compliance to High Blood Pressure Therapy Scale
This questionnaire was adapted from a previous study by Kim et al. 11 that assessed antihypertensive therapy adherence in predominantly black populations. It is a 14-items scale used to assess patients' behaviors for three important behavioral domains of high BP treatment: (1) reduced-sodium intake, (2) appointment keeping, and (3) medication taking. In this study, the only influential factor that could be interpreted in acceptability, reliability, and validity analysis was the medication-taking subscale (Table S1).
Thus, we simplified the 14-items Hill-Bone Scale to an 8-items scale for the assessment of medication intake behavior. This eightquestions item is similar to the short-form scale used by previous studies. 11,12 The internal consistency and reliability of the scale were shown by a Cronbach's α (0.763) and mean inter-item correlation (0.243) ( Table S1). The total score ranged from 19 to 32 (mean = 28.9797) with higher scores indicating good adherence.
A value below or equal to the fifth percentile which is equivalent to ≤80% (mean − 2SD) of the total score was used to define medication nonadherence.

| Perceived Barriers to Therapy Compliance Scale
The questionnaire consisted of nine items that assessed perceived barriers to medication adherence. The questionnaire was designed to assess four domains of medication nonadherence; perceived benefits of medication (three items), barriers to medicine accessibility (two items), barriers to lifestyle and dietary practices (two items) as well as barriers to alcohol and smoking cessation (two items). The reliability of the scale ranged from 0.621 to 0.800 (Table S2). Informed consent was obtained from all participants and confidentiality was assured.

| Data analysis
Data analyses were performed using SPSS v. 25. Descriptive statistics in percentages and cross-tabulation were used to evaluate demographic and adherence status. Inferential statistics to examine the relationships between adherence and perceived barriers to adherence were computed using the Spearman rank correlation and logistic regression analysis. Also, univariate and multivariate analysis was used to examine factors associated with medication nonadherence.
All factors associated with nonadherence at a p < 0.1 were included in a prediction model, and the results were presented. p < 0.05 were considered statistically significant.

| RESULTS
A descriptive summary of sociodemographic and medication history is shown in Table 1. Participants aged 50-59 years and 60-69 years constituted 37% and 39% of the study sample. Also, female participants mainly were represented (69.5%). Also, most of the respondents have been on treatment for either 8-10 years (32.5%) or above 10 years (37.8%). Table 2 summarizes the medication history of the study participants. More than half of the respondents did not know the names of their current medications. Most of the respondents were on dual therapy (36.2%), followed by three-drug treatment (27.6%). A majority (69.9%) had ever forgotten to take their BP medicine. Frequently perceived signs/symptoms of antihypertensive medications were headaches (26.4%), followed by muscle pain (18.3%), tiredness (11.0%), decreased sexual desire or ability (9.8%), poor sleeping (8.5%), frequent urination (7.7%), palpitations (6.5%), and swollen feet (4.9%).
The response frequencies for the 8-items Hill-Bone Medication Compliance subscale and Perception of Barriers to High Blood Pressure (BP) Therapy Compliance Scale are listed in Table 3. Most study participants indicated that they either forget to take their medications (64.2%) or decide not to take their medication (83.3%). The majority of the respondents opted for answers "none of the time" in all domains of the Hill-Bone subscale. The option "not at all" recorded the highest score on all the fields of the perceived barriers on the compliance scale ( Figure 1).
The majority (91.5%) of the respondents were adherent to current medications, whereas 8.5% showed some level of nonadherence to current medication taking Table 4 shows the correlation of the Perceived Barriers to Medication Adherence Scales and Hill-Bone Medication Adherence subscale. Perceived noneffectiveness of medication significantly correlated negatively with medication adherence score (ρ = −0.50, p < 0.001). Also, barriers to alcohol and smoking cessation significantly negatively correlated with medication adherence score (ρ = −0.25, p = 0.001). Tables S3   and S4. There was no significant association observed between sociodemographic characteristics and medication nonadherence among the study participants (Table S3). In Table S4, total prescribed medication (p = 0.011) and appointment schedules (p = 0.031) were significantly associated with adherence status. In a hierarchy regression analysis, as shown in Table S6, perceived barriers to medication noneffectiveness, lifestyle and dietary changes, alcohol and smoking cessation, and perceived symptoms of palpitations and muscle pain were associated with lower medication adherence scores (Table 5).

| DISCUSSION
Medication nonadherence presents a significant limitation in combating public health challenges in both developed and developing countries. 13 It is an active decision of a patient, relatively to misunderstandings of the condition and general disapproval of medication, but mostly taken to facilitate daily life or minimize complications. 14 On the contrary, adherence to antihypertensive medication is associated with significantly lower total healthcare cost, overall odds of reduced cardiovascular-related hospitalizations, and lower emergency department visits. 15 This study assessed the correlates of medication adherence among hypertensive clients in a Ghanaian population. We observed that a significant percentage (approximately 70%) of the hypertensive clients have stopped taking their medication at least within the last 3 months. This action taken by clients has been associated with adverse effects on the medication-taking behavior of clients. However, medication nonadherence was relatively lower (8.5%) among them. This finding can be attributed to the fact that most (74.9%) of the study participants decidedly skip their BP medicine before their scheduled appointment with the doctor. Moreover, most of the study participants indicated These reported signs were associated with medication nonadherence. Gebreyohannes et al. 4 reported that perceived symptoms of tiredness, muscle pain, and poor sleep attributed to medicines are associated with poor adherence rates. Also, Tedla and Bautista 23 reported that 85% of hypertensive clients experienced side effects, which was significantly associated with medication nonadherence.
Moreover in a systematic review and meta-analysis by van der Laan et al. 24 and AlGhurair et al., 25 drug side effects were identified as one of the key factors with consistent significant relationships with medication nonadherence. Hypertensive patients frequently report symptoms that are also reported by normotensive patients. Although to a larger extent, these perceived symptoms are true for antihypertensive medication treatment. 26 A previous study has also stated that increased specific concerns about medication can predict poor adherence, which is similar to our findings. 27 This finding can be interpreted that, in the Ghanaian society if there is a minor ailment, a patient will just attribute it to their medications without the necessity of reporting to the healthcare provider. These perceptions can create the belief that they are not worried about taking prescribed medicine leading to poor adherence.
The study also observed that patient sociodemographic factors were not associated with medication adherence. In the reports of Inkster et al., 17 no significant association was reported between adherence to medication and sociodemographic variables, comorbidities, or the number of antihypertensive drugs taken, which is partly consistent and partly inconsistent with our findings. We also observed that barriers to smoking and alcohol cessation and not knowing total prescribed medications were associated with medication nonadherence. The total number of medications taken by the patient was not associated with adherence. Some studies have partly evaluated these findings. 17,24 The findings of barriers to smoking and alcohol cessation associated with medication nonadherence have not been justified. In previous unrelated clinical evaluations and computer-based simulations, alcohol, and smoking affect medication adherence in both HIV-infected and -noninfected clients. 28,29 This finding in HPT may have clinical implications concerning optimal treatment for hypertensive clients who also smoke or consume alcohol. Thus, better knowledge about HPT and its management and clients' perceived benefits of medication could contribute to better adherence.
The study has a limitation with a small sample size which had an effect on the statistical power of the regression model performed. Also, the Hill-Bone Scale for measuring adherence to medication was self-reporting, which may not provide a true picture of actual adherence. Thus, the percentage of the nonadherence rate may either be underestimated or overestimated due to recall and social desirability bias from the clients. This may be on the part of the client trying not to disappoint their doctors or the researchers. Moreover, the cut-offs used for defining nonadherence both with Hill-Bone subscale score were predetermined (as an estimate of <80% of the total score). However, there is no standard cut-off for these measures.

| CONCLUSION
In conclusion, the study observed high adherence to antihypertensive medication among hypertensive clients in a Ghanaian population. We also identified that medicine-related factors negatively impact adherence to medications. Most importantly, palpitations, poor sleep, and decreased sexual desire or ability significantly predicted lower adherence. Thus, these symptoms could serve as markers to screen outpatients at high risk of nonadherence. Moreover, clients with significant barriers to smoking and alcohol and smoking cessation were likely nonadherent to medications. Obirikorang had full access to all of the data in this study and takes complete responsibility for the integrity of the data and the accuracy of the data analysis.